The present invention is directed to an ion processing apparatus for processing a target with ions, and more particularly to an ion processing apparatus including a plasma ion source and a mass spectrometer for ion deposition for depositing ions onto the surface of a target to form a thin film on the target, for ion implantation for implanting ions into a target to modify the composition or properties of the target, or for isotope separation to prepare bulk amounts of highly enriched, stable isotopes.
Ion processing apparatuses for processing a target with ions are known in the art. For example, U.S. Pat. No. 4,766,320 discloses an ion implantation apparatus including an unspecified ion source and a magnetic-sector mass spectrometer. Japanese Patent Application Laid-Open No. 1-95458 discloses an ion implantation apparatus including an ion source and a quadrupole mass spectrometer. Absent an English translation of this reference, it is unclear if a particular type of ion source is specified.
Further, U.S. Pat. No. 4,897,282 which is assigned to the assignee of the present application discloses an apparatus for forming a thin film on a target. Finely divided particles of a coating material to be deposited on a target are introduced into an inductively coupled plasma (ICP) torch in a stream of a carrier gas such as argon. The coating material is vaporized by plasma heating in the ICP torch. The vaporized coating material passes through a first orifice in a sampler into a first vacuum zone and then through a second orifice in a skimmer into a second vacuum zone. The vaporized coating material is cooled below its melting temperature as it passes through the first and second vacuum zones, and is subsequently deposited on a target disposed in the second vacuum zone in a solidified atomic, ionic, and/or molecular form to form a thin film.
In the apparatus of U.S. Pat. No. 4,897,282, the coating material is deposited directly on the target after it passes through the second orifice. No provision is made to guarantee the purity of the deposited coating material. This requires the use of a high-purity coating material if a high-purity thin film is desired. Also, no provision is made to remove unwanted background species passing through the second orifice such as neutral argon or argon ions from the plasma. Furthermore, while the stoichiometry of the thin film can be controlled by controlling the reaction conditions in the plasma, it is difficult to achieve precise control of the stoichiometry in this manner.
Ion processing apparatuses for isotope separation are also known in the art. Such an apparatus which uses a plasma ion source and a magnetic-sector mass spectrometer is disclosed in K. Eberhardt et al., "A Microwave Induced Plasma Operated at Atmospheric and Low Pressure as an Ion Source for a Mass Separator", Soectrochimica Acta, Vol. 47B, No. 1, pp. 89-94, 1992. This apparatus employs a microwave-induced plasma and is intended primarily for separation of radionuclides such as .sup.235 U; thus, the sample is introduced as a particle beam from a nuclear reactor. In contrast, the present application deals primarily with an inductively coupled plasma and is intended primarily for separation of stable isotopes introduced by nebulization or other simple sample introduction means.